By PDC’s Senior Weather
Specialist Glenn James
The Pacific Disaster Center’s (PDC Global) Wednesday, January 31, 2024, Tropical Cyclone Activity Report…for the Pacific Ocean, the Indian Ocean, and adjacent Seas
Current Tropical Cyclones:
Tropical Cyclone 09S…is located approximately 617 NM east of St Denis, La Reunion Island
Northeast Pacific Ocean:
The North Pacific hurricane season officially ended on November 30, 2023. Routine issuance of the Tropical Weather Outlook will resume on May 15, 2024. During the off-season, Special Tropical Weather Outlooks will be issued as conditions warrant.
The eastern Pacific basin hurricane season was above normal, with 17 named storms, of which 10 were hurricanes and eight of those major hurricanes.
From August 16 to 21, Tropical Storm Hilary brought widespread heavy rainfall and flooding to Southern California, with some areas receiving up to 600% of their normal August rainfall. Hilary resulted in the first ever issuance of Tropical Storm Watches and Warnings for the Southern California coastline by NOAA’s National Hurricane Center. In addition, the Center distributed key hazard focused messages for Hilary in Spanish through the agency’s new language translation project.
Hurricane Otis made landfall near Acapulco, Mexico, on October 25 as a category-5 hurricane, with sustained winds of 165 mph. Otis holds the record as the strongest land falling hurricane in the eastern Pacific, after undergoing rapid intensification in which wind speeds increased by 115 mph in 24 hours.
Central North Pacific:
The central North Pacific hurricane season officially ended on November 30, 2023. Routine issuance of the Tropical Weather Outlook will resume on June 1, 2024. During the off-season, Special Tropical Weather Outlooks will be issued as conditions warrant.
The central Pacific basin had a near-normal season with four tropical systems traversing the basin.
Hurricane Dora, a category-4 storm, passed south of Hawaii in early August, marking the first major hurricane in the central Pacific basin since 2020. The strong gradient between a high pressure system to the north and Dora to the south was a contributing factor to the wind-driven, fast-moving wildfires in Hawaii.
Western Pacific, Indian Ocean and adjacent Seas:
South Indian Ocean…
Tropical Cyclone 09S
According to the JTWC warning number 3, sustained winds are 35 knots…with gusts to near 45 knots.
Tropical cyclone 09S continues to struggle to consolidate a vertically aligned vortex, as depicted in animated multi-spectral satellite imagery (msi), which shows a completely exposed and decoupled low level circulation center (llcc) displaced to the west of remnant convective blow off.
The most recent msi however, shows a blossoming of deep convection in close proximity of the llcc, suggesting that the system may finally be poised to symmetrize. A satellite image showed the low-level banding features wrapping into the well-defined llcc and developing convection confined to a small area just east of the llcc.
The environment is marginally favorable with warm sea surface temperatures, and good poleward outflow, constrained by dry mid-level air to the west and moderate mid-level westerly shear and convergent upper-level flow to the west.
While the shear analysis indicates just 10 knots of northwesterly shear, the GFS model soundings suggest mid-level shear up to 30 knots which appears generally to be supported by the satellite depiction. The system is currently in a weak steering pattern, with no clear-cut steering mechanism and is thus meandering rather aimlessly east of Port Mathurin.
The weak steering pattern is anticipated to remain firmly in place through the next 36 hours and TC 09S will continue to meander inside this pocket of weak steering through at least 36 hours. By 48 hours, a major shortwave trough will move in from the west and combine forces with a building ridge to the northeast and eject TC 09S onto a southeastward track. After 48 hours and through the remainder of the forecast, TC 09S will accelerate along the tight gradient between the ridge and the deepening trough, reaching track speeds approaching 30 knots by the end of the forecast period.
In terms of intensity, everything depends upon the vortex axisymmetrization process. The latest ships guidance suggests a slight reduction in the deep layer shear, which could allow for the vortex to align vertically and the convection to sustain itself. However, this would be offset by a localized reduction in sea surface temperatures due to upwelling as the system remains quasi-stationary. Around 36 hours, the shear is expected to reach a minimum while poleward outflow begins to really ramp up as it taps into the divergent flow ahead of the approaching trough, allowing for a brief period of intensification up to 40 knots.
By 72 hours shear picks up sharply, to at least 40 knots and comes to dominate the outflow and the system will be sheared apart. At this point the race will be on to see which happens first, dissipation or extratropical transition (ett). The current forecast calls for both to occur simultaneously no later than 96 hours, but the system could dissipate well before this point, especially if it fails to organize in the near-term.
Southwest Pacific Ocean…
>>> There’s an area of disturbed weather being referred to as the Remnants of 07P…which is located approximately 48 NM south-southeast of Mornington Island, Australia.
Animated multi-spectral satellite imagery depicts a partially exposed low-level circulation center (llcc) with persistent deep convection over the northern and western peripheries of the circulation center.
Environmental analysis indicates that the remnants of 07P is in a marginally favorable environment for development with robust equatorward outflow aloft, moist air in the area, and low surface pressures offset by moderate to high (20-25 knot) vertical wind shear. Recent observations from Mornington Island, to the north, show westerly winds of 26 knots.
The system is currently located along the southern coast of the Gulf of Carpentaria and global models have the system tracking slowly and erratically over the next 36-48 hours with a brief period where the system could reach weak tropical cyclone strength before tracking back southward.
Maximum sustained surface winds are estimated at 25 to 30 knots.
The potential for the development of a significant tropical cyclone within the next 24 hours is upgraded to high.